send proximity_out in proximity in for tablet_v2
send proximity_out in proximity in for tablet_v2

When the proximity_in event is sent for tablet_v2 and there's already a
surface that currently has tablet (tool) focus, it should be told that
this is no longer the case, so we need to send the proximity_out event.

SirCmpwn/wlroots,ascent12/wlroots,swaywm/wlroots,swaywm/wlroots,ascent12/wlroots